Automatic control of variable physical conditions



Dec. 12, 1944. I "H. w. matrrr 2,364,718

AUTOMATIC CONTROL. O1" VMIABLI' PHYSICAL CONDITIONS Filed m. 9,194:

A a/W 520M *MW ?atented Dec. 12, 1944 AUTOMATIC GONTRDL F VARIABLE PHYSICAL CONDITIONS Harold William Ibbott, London; England, assignor to Negretti Zambra, London, England Application February 9, 1943, Serial No. 475,289 In Great Britain July 1, 1942,

I Claims.

sive to changes in the condition to be controlled and exerting a force against resistance to its displacement which varies according to the state of said condition, mechanical linkage serving to transmit from a force-applying device resistance to said displacement, means adapted, when theiorce exerted by said primary device is out of balance with the resistance thereto, to vary the state of said condition in the sense of restoring balance, and at least one secondary device responsive to changes in another factor or factors required to be taken into account in the determination of the desired state of the firstmentioned condition, which latter device operates on the mechanical linkage to vary its leverage.

The secondary device or devices may be adapted to operate on the mechanical linkage without receiving or transmitting any substantial reaction from or to the force being transmitted through the linkage to or from the said forceapplying device.

Preferably the mechanical linkage comprises a pivoted frame or like element about the axis of which there-are opposed moments of forces, one of these forces being applied to the frame or like clement through a member pivoted about an axis inclined to the axis of the frame or like element, so that the distance of the line of action of the force from the axis of the frame or like element varies when the pivoted member is rocked, and the member is adapted to be rocked through the agency of the said secondary device.

The secondary device(s) may operate on the mechanical linkage through the intermediary of means which as the respcnse(s) of the devlce(s) continue in the same sense produce a non-proportional and/or eventually a. reverse movement of the rocking member.

As a further or alternative means of introducing the effect of another factor, the force of the force-applying device may beadapted to be varied at will and/or automatically in accordance with a change in a factor required to be taken into account in the control. Thus the forceapplying device may comprise a plurality of springs capable of individual and several adjustments by means responsive to a change in a factor or to the will of an operator.

The invention is illustrated in the accompanying drawing which shows in perspective one form of control apparatus suitable for carrying the invention into effect.

In the drawing a diaphragm or capsule I, responsive to pressure changes which may occur in or in relation to the operation of machinery, and which pressure may be directly or indirectly produced from any physical condition in question, is connected to a frame 2 free to rotate about a vertical axis Y-Y|. is a bell crank lever 3 pivoted to rotate about a horizontal axis. A strut 4, serving to transmit an opposing force to the frame 2, bears horizontally on the side of one arm of the bell crank lever 3. This strut at its other end bears on the side of one end of another bell crank lever 5 pivoted on a. second frame 6 so as to be rotatable about a horizontal axis. The second frame 5 pivots about a vertical axis Y2-Y3 and supports a further bell crank lever l, at the opposite side of the frame to the bell crank lever 5 against which the said other end of the strut 4 bears, and this further bellcrank lever l is pivoted about ahorlzcntal axis. A second strut 8 bears at one end on the side of the bell cranklever 'l and at the other end upon a pivoted lever ,9 which is directly subjected to the force of two springs III, II.

Normally, i. e. when a state of equilibrium exists, the two first mentioned bell cranklevers 5, 3 pivot on a common horizontal axis X-Xl whilst the bell crank lever 1 pivots on an axis X2-X3 passing through the point of contact of the remote end of the strut 8 where itbears upon the pivoted lever 9.

An extension of the second frame 6 carries an insulated contact l2 arranged to operate between high and low electric contacts i3, I! respectively of a reversible electric motor i5. The movement required by the insulated contact 52 to make" from mid-=oilf position is very small and the pivot points of the bell crank levers'do not move sensibly from their normal axes.

When a state of equilibrium exists the force from the diaphragm or capsule l is in balancewith the reactions of the springs In, H and contact i2 is at "mid-off position. Whilst this condition is maintained the force of the springs is confined solely to react on the diaphragm or capsule, and in no way through the bell crank levers to the means for rocking the latter, to which reference will now be made.

Each of'the bell crank levers is adapted to be Supported by the frame 2 i rocked responsively to factors or conditions which 1 are required to be taken into account in the conf trol. Such factors or conditions may exert their influence through diaphragms or capsules l6, l1

connected to the bell crank levers 3, 5 and I directly or through linkage so as to apply the rocking force in a vertical line so that the .dis-

placement of the frames 2 and 6 on which the 1 bell cranklevers are pivoted will not react upon the secondary diaphragms or capsules.

In the arrangement shown thediaphragm or capsule I 6, responsive to one secondary factor,

is provided with linkage indicated generally at l8 which causes the rotation of a spindle 19 connected by links 20, 2I'to the bell crank levers 3 and 5. A stop 22 limits the rotation of the spindle IS in one direction and the rotation of the spindle in the other direction takes place i 3 against the action of a spring 23, which tends to return the spindle back to its position against the stop 22.

The'diaphragm or capsule H which is responsive'to a further secondary factor is connected by means of linkage 24 to the bell crank lever I. It will be understood that the words vertical .and horizontal are used in the above description in a relative sense.

The effect of the rockings of the bell crank levers 3, 5 and I is to alter the radius of application of the forces transmitted from the springs I0, H to the primary diaphragm or capsule l by bringing the struts 4 and 8 nearer to or further away from the pivotal axes of the frames 2 and 6.

It will therefore be understood that a change in one or other of the secondary factors, as well as a change in the primary condition to be controlled, will bring about a, condition of unstable equilibrium, and when this occurs the insulated 1 contact l2 will make electrical connection to cause the electric motor l5 to'operate' in one direction or the other to actuate means for controlling the primary condition to which the pri- 7 strength of the spring II. A cam lever 25, connected to an operative element in connection with the machinery or apparatus in which the control is being exercised,is arranged by means of a rod 26 to take off the force of the spring H] from the lever 9 upon which it bears. Another cam lever 21 is adapted by means of a rod 28 to change the force of one or both springs from the lever 9 upon which they bear, and in this way the effect of the control apparatus may be modified on demand.

The control apparatus according to the presing the temperature of internal combustion engines, particularly of aircraft, by controlling the amount of cooling air used, applying the differential pressure set up by the passage of cooling air to operate the primary diaphragm or'capsule, and imposing upon the control the effects of other variable factors required to affect the regulator to control the temperature of the engine, such as V boost pressure, cooling air temperature, altitude, supercharger gear and pilot's will.

I claim:

1. Automatic control apparatus comprising a primary device responsive to changes in the condition to be controlled and exerting a force against resistance to its displacement which varies according to the state of said condition, mechanical linkage serving to transmit from a force-applying device resistance to said displacement, means adapted, when the force exerted by said primary device is out of balance with the resistance thereto, to vary the state of said condition in the sense of restoring balance, and atleast one secondary device responsive to changes in another factor or factors required to be taken into account in the determination of the desired state of the first-mentioned condition, which her being rocked through the agency of the said latter device operates on the mechanical linkage to vary its leverage, said mechanical linkage comprising a pivoted frame about the axis of which there are. opposed moments of forces, a member to apply one of these forces to the frame, said member being pivoted about an axis inclined at approximately right angles to the axis of the frame so that the distance of the line of action of the force from the axis of the frame varies when the pivoted member is rocked,.the said forces being exerted by the said primary device and said force-applying device, and the said pivotal memsecondary device.

2. Automatic control apparatus as claimed in claim 1 in which means are provided for varying the strength of the force applied by the'forceapplying device.

3. Automatic control apparatus as claimed in claim 1 in which means are provided for automatically varying the strength of the force applied by the force-applying device in accordance with a change in a factor required to be taken into account in the control.

4. Automatic control apparatus as claimed in claim 1 in which the force applying device cornprises a plurality of springs capable of individual and several adjustments.

5. An automatic control apparatus as claimed in claim 1, in which the said secondary device operates upon said pivotedmember so that as itsresponse continues in the same sense it produces ent invention is particularly suitable for regulata non-proportional movement of the said pivoted member.

HAROLD WILLIAM IBBO'I'I. 

